The present application is a National Stage Application of International Application No. PCT/EP01/00385, filed Jan. 13, 2001. Further, the present application claims priority under 35 U.S.C. xc2xa7 119 of German Patent Application No. DE 100 03 383.0 filed on Jan. 26, 2000.
1. Field of the Invention
The invention relates to a method for determining a characteristic value for the binding force potential of paper fibers in a fibrous suspension prepared for paper manufacture.
2. Discussion of Background Information
In paper manufacture it is known that paper fibers are placed in an aqueous fibrous suspension on the paper machine and dewatered. The paper fibers touching each other thereby develop binding forces which ultimately lead to the formation of a firmly cohesive sheet of paper. The possibility of developing such binding forces, i.e., the binding force potential, depends on a plurality of parameters. The most important are fiber condition and fiber size, as well as the chemical and material environment in the suspension. Improving the binding force potential is often associated with costs for raw material quality, processing and the use of chemical aids. It is therefore desirable to be able to determine the binding force potential in a timely manner, i.e., before the actual paper production, so as to be able to optimize the entire process.
The invention therefore provides for a method in which the binding force potential of paper fibers in an aqueous suspension can be characterized. In particular, the invention makes possible the detection of deviations from the desired binding force potential in a timely manner. The measurement leads to quick measurement readings.
According to one embodiment, there is provided a method for determining a characteristic value for the binding force potential of paper fibers in a fibrous suspension prepared for paper manufacture, characterized in that the air content of the fibrous suspension is measured and that the characteristic value is derived therefrom.
The air content can be measured at a measuring point in the fiber stock preparation process at which the fibrous suspension has the stock composition necessary for paper manufacture, without the air content having been adjusted by a corresponding deaeration process. The air content can be measured in the approach flow system of a paper mill after the mixing pump in which the fiber stock is mixed with diluting water. The air content in the approach flow system of a paper mill can be measured before the mixing pump in which the fiber stock is mixed with diluting water. After measuring the air content, the fibrous suspension can be deaerated by way of a vacuum. Several sorts of fiber stock can be used for paper manufacture at the same time, and that the air content can be measured separately in the sorts. The characteristic value for the binding force potential can be assigned to the air content with the aid of corresponding empirical values. The empirical values can be determined by measuring the strengths of the sheets formed from the suspension. The empirical values can be assigned to the paper machine by determining the runability achieved with the fibrous suspension. An amount of strengthening chemicals and/or retention agents added to the fibrous suspension can be adjusted such that a characteristic value which was stipulated as useful is maintained. The amount of strengthening chemicals and/or retention agents added to the fibrous suspension can be minimized according to the demands on runability.
Particularly useful measuring data are obtained at the point where no measures have yet been taken for the effective deaeration of the fibrous suspension. Here, the air content can freely adjust according to the fiber technology and chemical parameters of the fiber stock prepared for paper manufacture. Surprisingly, the correlation of the air content measured at this point and the binding force potential can be defined with sufficient accuracy that an early prediction can be made of certain paper properties to be expected. This correlation can be easily determined, e.g., by way of empirical measurements even without all causalities being known. It can be assumed that the air content itself is not important for binding force potential, but it serves merely as an indicator. In many cases a higher binding force potential can be established with a higher air content.
In practice the air content measurement is made, e.g., in the approach flow system of the paper mill after the mixing pump in which the paper stock is mixed with the diluting water and brought to the required stock consistency. If the paper or cardboard is to be produced from different sorts, the characteristic values for these sorts can also be separately determined and corrections made individually.
Various possibilities are conceivable for reacting to the deviation of the characteristic value from its set value: the use of chemical agents, changing the fiber treatment or composition or adjusting the paper machine up to reducing the wire speed.
With the aid of the method according to the invention, the paper machine process can be brought up to optimum runability on the paper machine simply and economically. It makes it possible to correct the binding force potential in a timely manner, i.e., before a break has occurred on the paper machine. It is known that the prevention of breaks is a very important economic advantage in paper manufacture.
The invention also provides for a method for determining a characteristic value for a binding force potential of paper fibers in a fibrous suspension, the method comprising measuring an air content of the fibrous suspension and deriving the characteristic value from the measuring.
The method may further comprise feeding the fibrous suspension to a paper machine. The measuring may comprise measuring the air content at a measuring point arranged before the fibrous suspension is fed to a paper machine. The method may further comprise subjecting the fibrous suspension to deaeration. The measuring may comprise measuring the air content at a measuring point arranged before the fibrous suspension is subjected to deaeration. The measuring may occur at a point in an approach flow system of a paper mill. The point may be arranged downstream of a mixing pump that mixes a fiber stock with diluting water. After the measuring, the method may further comprise deaerating the fibrous suspension using a vacuum. The measuring may comprise measuring an air content of the fibrous suspension of each of several sorts of fiber stock. The measuring an air content of the fibrous suspension of each of several sorts of fiber stock may occur at the same time. The measuring an air content of the fibrous suspension of each of several sorts of fiber stock may occur separately.
The method may further comprise assigning the characteristic value to the air content using corresponding empirical values. The method may further comprise determining the empirical values by measuring strengths of sheets formed from the fibrous suspension. The method may further comprise determining a runability of the fibrous suspension and assigning the empirical values to a paper machine based upon the determining. The method may further comprise adding an amount of strengthening chemicals and/or retention agents to the fibrous suspension. The method may further comprise adjusting the amount of strengthening chemicals and/or retention agents based upon the characteristic value. The method may further comprise maintaining the amount of strengthening chemicals and/or retention agents based upon the characteristic value. The method may further comprise minimizing the amount of strengthening chemicals and/or retention agents added to the fibrous suspension. The method may further comprise determining a runability and minimizing an amount of strengthening chemicals and/or retention agents added to the fibrous suspension based upon the runability.
The invention also provides for a method for determining a characteristic value for a binding force potential of paper fibers in a fibrous suspension, the method comprising feeding the fibrous suspension to a paper machine, measuring an air content of the fibrous suspension before the feeding, and controlling the characteristic value based upon the measuring.
The method may further comprise forming the fibrous suspension by mixing prepared fiber stock and water. The water may comprise backwater from a paper machine. The measuring may comprise measuring the air content at a measuring point arranged before the fibrous suspension is fed to a deaeration device. The method may further comprise, after the measuring, subjecting the fibrous suspension to deaeration. The measuring may comprise measuring the air content of a prepared fiber stock. The measuring may comprise measuring the air content of a sample of prepared fiber stock. The measuring may comprise measuring the air content after the fibrous suspension is formed by mixing a prepared fiber stock with water and before the fibrous suspension is subjected to deaeration. The measuring may occur at a point in an approach flow system of a paper mill. The point may be arranged downstream of a mixing pump that mixes a fiber stock with diluting water. After the measuring, the method may further comprise deaerating the fibrous suspension using vacuum.
The method may further comprise controlling a proportioning pump using a regulator which is connected to a measuring point via a signal line. The method may further comprise determining empirical values by measuring strengths of sheets formed from the fibrous suspension. The method may further comprise determining a runability of the fibrous suspension and assigning the empirical values to a paper machine based upon the determining. The method may further comprise regulating an amount of strengthening chemicals and/or retention agents added to the fibrous suspension. The method may further comprise adjusting the amount of strengthening chemicals and/or retention agents based upon the measuring. The method may further comprise maintaining the amount of strengthening chemicals and/or retention agents based upon the measuring. The method may further comprise minimizing an amount of strengthening chemicals and/or retention agents added to the fibrous suspension based upon the measuring. The method may further comprise determining a runability and minimizing an amount of strengthening chemicals and/or retention agents added to the fibrous suspension based upon the runability.
The invention still further provides for a system for determining a characteristic value for a binding force potential of paper fibers in a fibrous suspension, the system comprising a mixing device which mixes a prepared fiber stock and water to form the fibrous suspension, a deaeration device which removes air from the fibrous suspension, a measuring device which measures an air content of the fibrous suspension before the deaeration device, and a regulator connected to the measuring device and a proportioning pump.